Search PubMed⌕ Search

Biomedical subjects

E Decuypere

Publications and source records attributed to E Decuypere.

At least 109 records · Page 6Linked to original sources
PubMed1999

Role of melatonin in the control of growth and growth hormone secretion in poultry.

The pineal hormone melatonin controls reproduction of photoperiodic mammals and is an integral part of the circadian organization in birds. Recent findings indicate an involvement of this hormone also in more basic physiological processes, including growth, development, and aging. Melatonin may modulate growth in poultry through interaction with transcriptional factors, through interaction with hormones involved in growth control, and by modulation of energy metabolism and decreasing physical activity. Our studies showed that a single melatonin injection increased plasma growth hormone (GH) concentrations in the Japanese quail. Specific serotonin receptor blocker ketanserin did not preclude a stimulatory action of melatonin on GH synthesis. Serotonin agonist quipazine increased GH levels but failed to enhance the stimulatory effect of melatonin. Pretreatment with melatonin in drinking water did not affect the magnitude of the GH response to subcutaneous (s.c.) administration of thyrotropin releasing hormone (TRH) that considerably stimulated GH secretion. Present data suggest that melatonin modulates rather central neural pathways involved in the control of GH synthesis at the hypothalamic level than the sensitivity of the pituitary gland.

Animals↗
PubMed1999

The role of the somatotrophic axis in the metabolism of the chicken.

As it is for mammalian species, growth hormone (GH) is indispensable for normal growth and development of avian species. In contrast to mammals, exogenous GH administration has little, if any, potential for improving the growth rate and feed efficiency of rapidly growing broilers; it is more likely to do so in older birds. This is at least partly because of age-related changes in tissue GH-binding activity and GH-receptor mRNA expression. The effects of GH on lipid deposition depends on the age of the bird and pattern of GH administration. Pulsatile, but not continuous, GH administration to older broilers seems to reduce fat deposition. As in rats, the bioactivity of GH might also depend on the pulse-induced cyclicity in GH receptors and GH-binding proteins. In chickens, GH is also a very potent lipolytic hormone, but seems to have no diabetogenic effect, which is reported in mammalian species. Both insulin-like growth factors have apparently no growth-promoting effects in normal growing broilers, but seem to have opposite effects on fat deposition. In contrast to GH, both insulin-like growth factors have a marked hypoglycemic effect. Whether all these effects are direct effects, or are mediated by secondary mechanisms, awaits further investigations.

Adipose Tissue↗
PubMed1999

Insulin-like growth factors in the regulation of avian ovarian functions.

In the past three decades, overwhelming evidence has accumulated to show that insulin-like growth factor (IGF)-I and -II, their receptors and binding proteins (IGFBP) (the IGF system), have major roles to play in the regulation of ovarian function in mammals. Although studies in birds did not start until 5-6 years ago, the limited information thus far available suggests that the IGFs act as autocrine/paracrine regulators of follicular growth and differentiation, just as observed in mammals. The genes for IGF-I and -II, type-I IGF receptor, IGFBP-2, and IGFBP-5 are expressed in both granulosa and theca cells of the chicken ovary. The mechanisms by which the IGF system controls ovarian function in the avian species are complex and involve interactions with the gonadotrophins (LH and FSH), growth hormone, and even other growth factors. Effects are different between strains and nutritional status.

Animals↗
PubMed1999

Measuring the mechanical stiffness of an eggshell using resonant frequency analysis.

1. A new method was introduced for the measurement of mechanical eggshell characteristics based on the analysis of the vibration response of a chicken egg excited with a non-destructive impact. Four major topics were examined. 2. The 3 dimensional vibration pattern of an intact chicken egg was described for the spherical vibration with the lowest resonant frequency. 3. The resonant frequency of this basic vibration mode and the total egg mass were used to calculate a dynamic stiffness value of the eggshell based on a mathematical mass-spring model. 4. A correlation analysis between this dynamic stiffness value and several common egg and eggshell variable was calculated. Pearson correlation coefficients between the dynamic stiffness and static stiffness, eggshell thickness at the equator, eggshell width and shape index were all significantly different from zero and were 0.71, 0.60, 0.43 and 0.51, respectively. 5. Graphical analysis of the static vs. the dynamic eggshell stiffness indicated that eggs with thick shells (>360 microm) had a higher static stiffness value than the dynamic stiffness measurement, whereas the static stiffness of eggs with thin shells (>300 microm) was lower than the dynamic stiffness. 6. The new vibration test method is a promising alternative for evaluating mechanical eggshell properties because of its non-destructive nature and brief measuring time.

Animals↗
PubMed1999

Evaluation of jojoba meal as a potential supplement in the diet of broiler breeder females during laying.

1. This study was undertaken to investigate whether jojoba meal can be used as a food supplement during the laying period of chickens. 2. The size of eggs laid were smaller and the overall production rate was lower compared to control birds on food without jojoba meal supplementation. Furthermore, both ovary and oviduct weights were lower in jojoba fed birds. 3. This lowering of egg size and production rate was caused by factors present in jojoba which interfere with follicle growth, yolk deposition, progesterone production and the follicular maturation processes, resulting in the ovulation of smaller follicles and a lower ovulation rate.

Animal Feed↗
PubMed1999

Hepatic concentration of heat shock protein 70 kD (Hsp70) in broilers subjected to different thermal treatments.

1. The relationship between repeated thermal treatments and hepatic synthesis of Hsp 70 was studied in broiler chickens. 2. Sixty broilers were submitted to 5 different treatments (12 birds each) from day 1 to day 42. Four groups were kept in a thermoneutral environment and subjected to 0, 1, 2 and 3 heat stress episodes at 35 degrees C for 4 h per week (TN-0, TN-1, TN-2 and TN-3, respectively). The last group (HT-35) was reared at a room temperature of 35 degrees C. 3. From 39 to 42 old, the birds experienced acute heat stress at 41 degrees C. Resistance to heat stress was evaluated by the time taken for rectal temperature to increase by 3 degrees C above the pre-treatment value. Livers were collected (before and after heat stress) and Hsp70 was determined using Western Blot analysis with monoclonal anti-Hsp70 antibody. 4. Resistance to heat stress and concentration of Hsp70 were higher in those birds subjected to more heat stress episodes during the experimental period (TN-3) and HT-35. A positive correlation was observed between Hsp70 concentration and the time taken for a 3 degrees C increase in rectal temperature (r = 0.42; P<0.01). 5. Exposing birds to episodes of heat stress (35 degrees C) during rearing may improve their resistance to acute heat stress, but the previous thermal history did not seem to influence the hepatocyte Hsp70 content after exposure to more severe heat stress (41 degrees C).

Analysis of Variance↗
PubMed1999

Performance and physiological variables in broiler chicken lines differing in susceptibility to the ascites syndrome: 1. Changes in blood gases as a function of ambient temperature.

1. Male broilers of 5 genetic stocks (A, B, C, D, E) selected in different ways for fast growth and low food conversion ratio (FCR) and differing in ascites sensitivity were subjected to 2 different ambient temperature step down regimens: high temperature (HT: 33 to 20 degrees C over 33 d) and low temperature (LT: 30 to 15 degrees C over 17 d). 2. Ascites incidence was recorded daily. Food intake and body weight gain were measured weekly and FCR was calculated. Heat production (Hp) was calculated using the comparative slaughter method. At 28 d venous samples were taken for blood gas analysis and haematocrit and relative heart, lung and liver weights were recorded. 3. Populations A and C showed the highest growth rates combined with a low FCR and a higher ascites incidence. A low FCR in these stocks was attributable to low values for Hp. These stocks also had low PO2 and high pCO2 in venous blood at low ambient temperature compared with other stocks. Stock B, which exhibited the slowest growth rate and the highest FCR, was not susceptible to ascites and showed higher Hp and PO2 and pCO2 at low ambient temperature. Populations D and E were intermediate for almost all variables. Heart and lung weights were both increased at LT, while liver weight did not differ between temperature regimes. 4. Our results show that a high haematocrit is not necessarily linked with an increased susceptibility to ascites.

Animals↗
PubMed1999

Performance and physiological variables in broiler chicken lines differing in susceptibility to the ascites syndrome: 2. Effect of ambient temperature on partial efficiencies of protein and fat retention and plasma hormone concentrations.

1. Male broilers of 5 genetic stocks (A, B, C, D and E), selected in different ways for fast growth and low food conversion rate (FCR) and differing in sensitivity to ascites, were subjected to 2 different ambient temperature (Ta) step-down programmes: normal (HT) and low (LT) Ta. 2. Ascites incidence was followed daily. Growth and food intake were measured weekly. Heat production (Hp), oxygen consumption (Oxc) and energy- metabolism parameters were calculated according to the comparative slaughter method. At week 4 blood samples were taken for the analysis of plasma T4, T3, growth hormone (GH) and insulin-like growth factor-I (IGF-1) concentrations. 3. Within-line changes of GH and IGF-1 point to the relative independence of both hormone concentrations. 4. Partial protein efficiency was higher in lines with lower GH, especially at LT. 5. The increase in plasma T3 concentration at LT was accompanied by a decrease in relative fat deposition from the increased energy expenditure. 6. The combination of fast growth and low FCR, linked to a low plasma T4 concentration at LT is indicative of a thyroid insufficiency which is related to an increased occurrence of ascites in these lines.

Adipose Tissue↗
PubMed1999

Effects of timing and duration of feed restriction during rearing on reproductive characteristics in broiler breeder females.

The objective of this study was to determine whether there exists a critical period during rearing when restricted feeding of broiler breeder hens can be most beneficial on subsequent egg production. Broiler breeder pullets were subjected to combinations of either ad libitum or restricted feeding during three periods before sexual maturity. Body weight gain, feed intake, and egg production were recorded. Ovary and oviduct weights were noted at age of first oviposition. At 15 and 18 wk of age and at age of first oviposition, chicken luteinizing hormone releasing hormone-I (cLHRH-I) in the median eminence and the levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the pituitary and plasma were determined. The results demonstrated that alternation between ad libitum and restricted feeding during rearing changed the growth curves of the birds. Feed restriction from 7 to 15 wk followed by either ad libitum or restricted feeding led to improved reproductive performance, suggesting that long-term feed restriction may not be necessary to attain good reproductive performance. The birds restricted from 7 to 15 wk of age had higher proportional weights of ovary (> or = 1.7%) and oviduct (> or = 1.58%) at age of sexual maturity. The cLHRH-I levels in the median eminence and gonadotrophin contents in the pituitary followed that of growth in response to feeding levels and timing of feeding and could be related to the timing of the onset of lay. At age of first egg, all groups had similar levels of cLHRH-I, LH, and FSH. However, no clear effect of level of feed intake or time period of restriction could be observed for plasma LH or FSH concentrations.

Animal Feed↗
PubMed1999

Metabolic disturbances in male broilers of different strains. 2. Relationship between the thyroid and somatotropic axes with growth rate and mortality.

Seven male broiler strains (Arbor Acres, Avian Farms, Cobb-500, Hubbard-Peterson, ISA, Naked Neck, and Ross) were compared for their growth rate, feed efficiency, and mortality due to sudden death and ascites. In addition, weekly plasma levels of thyroid hormones [3,3',5-triiodothyronine (T3) thyroxine (T4), T3: T4 ratio, growth hormone (GH), and insulin-like growth factor-I (IGF-I)] were determined. The highly productive, commercial strains were very similar in their endocrine profiles but differed markedly from the Naked Neck chickens. Naked Neck chickens were characterized by higher plasma T3 and lower T4 levels at similar ages as well as when compared on the same body weight basis. The present findings support the hypothesis that the slightly hypothyroid state of high productive broilers renders them more sensitive to metabolic disorders. Naked Neck chickens also had higher plasma GH levels than those of their age-matched commercial broilers. The coefficient of variation for GH was highest for Naked Neck chickens, which is indicative for an amplified GH burst amplitude. It may be stated that changes in plasma thyroid hormone concentration in indirect response to selection for low feed conversion and fast growth may be causatively linked to susceptibility for metabolic disturbances such as sudden death syndrome and ascites.

Aging↗
PubMed1999

A beta-turn endocytic code is required for optimal internalization of the growth hormone receptor but not for alpha-adaptin association.

Intracellular trafficking of GH and its receptor, more particularly the chicken GH receptor (cGHR), was examined in COS-7 cells using biochemical and structural studies. Internalization of radioactive GH by the cGHR is reduced as compared with the rat GHR. On the contrary, activation of gene transcription through Janus kinase-2 was similar for both species. Secondary structures of the cytoplasmic domain of chicken and rat GHR were compared, since beta-turns were reported as internalization signals. The substitution of Pro335-Asp335, present in mammalian GH receptors, with Thr307-Gln308 in the cGHR leads to the loss of a beta-turn within a conserved cytoplasmic region. Mutational analysis indicated that the lower rate of internalization of cGHR, as compared with mammalian GHR, was due to this motif. Our data further show that alpha-adaptin, a subunit of adaptor protein AP-2, associates with the GHR upon hormone stimulation. The clathrin-coated pit pathway therefore seems to be involved in the endocytosis of cGHR, as AP-2 is known to intervene in the recruitment of receptors to these pits. Interaction with alpha-adaptin may occur through a common epitope of the chicken and mammalian GHR, since receptors from both species bind similar amounts of alpha-adaptin; alternatively, two different epitopes with similar affinity may be involved. Therefore, not alpha-adaptin but an uncharacterized factor, presumably interacting with the identified beta-turn endocytic code, is responsible for the difference in internalization kinetics. Finally, the present study illustrates that functional amino acid motifs of receptors can be derived from comparative studies.

Adaptor Protein Complex alpha Subunits↗
PubMed1999

Differential effects of amount of feeding on cell proliferation and progesterone production in response to gonadotrophins and insulin-like growth factor I by ovarian granulosa cells of broiler breeder chickens selected for fatness or leanness.

Strain differences in reproductive performance were demonstrated between broiler breeder female chickens selected for growth (GL line) or for food conversion efficiency (FC line) and the improvement in reproductive performance due to feed restriction also differed significantly. Feed allowance effects on the maturation of ovarian follicles, the incidence of atresia and egg production differed between the two lines exposed to similar feeding protocols. Feed restriction reduced body weights significantly and to a similar extent in both GL and FC lines. The number of normal and atretic yellow follicles was significantly higher under ad libitum feeding and in GL line than it was in the FC line. In both lines, feed restriction decreased multiple ovulation and increased egg production. In culture, granulosa cells from the three largest follicles (F1, F2 and F3) increased progesterone production in response to LH, FSH and insulin-like growth factor I but responses were different between the GL and FC lines fed either ad libitum or restricted diets. Granulosa cells from the two or three largest follicles in GL and FC (ad libitum) lines produced similar amounts of progesterone in response to LH, FSH and insulin-like growth factor I whereas, in restricted birds, the progesterone production was of the rank order F1 > F2 > F3 in both lines. The responsiveness of the GL line fed ad libitum was higher for LH than for either FSH or insulin-like growth factor I but in the GL line fed a restricted diet, it was high for all the hormones. In the FC line, responses to LH, FSH or insulin-like growth factor I were high in ad libitum-fed birds, but low in birds fed a restricted diet for all hormones. Insulin-like growth factor I combined with LH or FSH significantly increased the progesterone production of granulosa cells from birds fed restricted diets of both lines and this effect increased with increasing follicular size. There was a lack of interaction between insulin-like growth factor I and LH or FSH in the regulation of progesterone production by birds of both lines fed ad libitum. Insulin-like growth factor alone or in combination with LH or FSH increased granulosa cell proliferation in birds fed ad libitum more than it did in birds fed restricted diets. The greater proliferation rate of granulosa cells of chickens fed ad libitum, in response to insulin-like growth factor I alone or in combination with gonadotrophins, leading to the simultaneous differentiation of two or three large follicles with high progesterone production in response to LH or insulin-like growth factor I, accelerates the rate of maturation of follicles. This may also be the major cause of erratic and multiple ovulations in broiler breeder female chickens fed ad libitum. In conclusion, insulin-like growth factor I, alone or in combination with LH or FSH, is an important component in the control mechanisms for follicular development in broiler breeder hens. It is this component that is targeted by feed allowance and inadvertently altered by selection for growth.

Analysis of Variance↗
PubMed1999

Effects of simmondsin on food intake, growth, and metabolic variables in lean (+/?) and obese (fa/fa) Zucker rats.

Incorporation of 2.5 g/kg of the anorexigen, simmondsin, in the diet resulted in food intake reduction in both lean and obese Zucker rats; however, the obese rats were much more sensitive to the food intake-reducing activity of simmondsin. In both obese and lean simmondsin-treated Zucker rats, growth was slower than in control rats, but was the same as that in pair-fed animals. The 24 h heat production pattern showed a smaller diurnal variation and a lower mean in obese rats than in lean rats. Food intake reduction, as a result of either simmondsin treatment or pair feeding, caused a decrease in mean heat production. Simmondsin treatment, but not pair feeding, caused a decrease in the diurnal variation of heat production. Plasma total cholesterol levels were increased in both simmondsin-treated and pair-fed obese and lean Zucker rats compared with control animals; this increase was mainly due to an increase in HDL-cholesterol levels. Blood leptin levels in both obese and lean rats decreased with decreased food intake and decreased fat deposition, but in obese rats, simmondsin treatment resulted in an additional decrease in leptin levels. It is concluded that the food intake-reducing effect of simmondsin is more pronounced in obese Zucker rats than in their lean littermates, and except for the simmondsin-specific effects on leptin and total cholesterol values in obese littermates, the effects of simmondsin are related to food intake restriction in obese and lean Zucker rats.

Acetonitriles↗
PubMed1998

Unidentified Factors in Jojoba Meal Prevent Oviduct Development in Broiler Breeder Females.

Supplementation of feed with jojoba meal, as a means for autonomous feed restriction, was successful in depressing feed intake and controlling body weight of broiler breeder pullets to the extent recommended by the breeder company. However, these broiler breeders never produced eggs. At the level of ovary, normal follicle development and maturation did occur. A considerable number of ovulations occurred which were not followed by oviposition. After ovulation, the ova could not be captured by the oviduct, because of the small size of the oviduct, resulting in "internal laying". The virtual absence of oviduct development cannot be explained presently but it must be due to some yet unidentified factor(s) in jojoba meal which prevent(s) the normal development of the oviduct. These factors may be acting by abnormally increasing plasma progesterone or triiodothyronin levels and/or directly by themselves interfering with oviduct development. The nature of these factors requires further investigations.

Journal Article↗
PubMed1998

The effect of food intake from 2 to 24 weeks of age on LHRH-I content in the median eminence and gonadotrophin levels in pituitary and plasma in female broiler breeder chickens.

The present study describes the effect of long-term food restriction on hypothalamopituitary function in the broiler breeder hen during the period prior to sexual maturity. From 1 week of age onward, chickens were divided into 3 groups: one group received food ad libitum (Ad lib); a second group was fed a restricted quantity of food (Res); and a third group was restricted to obtain an intermediate body weight (Int) in between groups one and two. The effects of these feeding regimes on hypothalamopituitary function were assessed by measuring the amounts of cLHRH-I stored in the median eminence (ME) and the pituitary content and plasma levels of gonadotrophins. The Res group had significantly lower levels of cLHRH-I in the ME compared to the Ad lib animals. In all groups, there was a major increase in cLHRH-I in the median eminence about 3 weeks before onset of lay. The age of first oviposition was delayed by 2 and 6 weeks in the Int and Res groups, respectively, compared to the Ad lib animals, indicating that body weight gain patterns are not directly related to the appearance of the first egg. The attainment of sexual maturity may be associated with a threshold value of cLHRH-I stored in the ME in the Ad lib and Int birds. The pituitary LH and FSH contents (after week 16) were positively related to the amount of cLHRH-I in the ME. Plasma FSH concentrations in Ad lib and Int chickens peaked about 3 weeks before the first oviposition and this prepubertal peak was associated with increased pituitary FSH and ME cLHRH-I. There were however no relationships between plasma LH concentrations and pituitary LH content and between plasma LH and cLHRH-I amounts in the ME. The present study demonstrates that the delayed sexual maturation, caused by a chronic food restriction, may be associated with (1) delayed ovarian and oviductal growth, (2) decreased cLHRH-I storage in the ME, and (3) lower levels of LH and FSH in the pituitary. These hormones were however not directly related to levels of food restriction.

Animals↗
PubMed1998

Reproductive performance of rats treated with defatted jojoba meal or simmondsin before or during gestation.

The effects on food intake, growth and reproductive performance parameters of defatted jojoba meal and pure simmondsin, an extract from jojoba meal, were compared in female Wistar rats. Rats fed 0.15% simmondsin or 3% defatted jojoba meal (equivalent to 0.15% simmondsin) for 8 weeks before conception showed a similar reduction in food intake (about 20%) and a similar growth retardation compared with controls. Both treatments induced a reduction in the number of corpora lutea on gestation day 16: this effect could be ascribed to the lower food intake before conception because it was also observed in rats pair-fed to the treated ones. Rats given feed containing 0.15% simmondsin or 3% defatted jojoba meal during days 1-16 of gestation showed a similar reduction in food intake relative to controls. Foetal and placental weights were reduced, relative to controls, to a similar extent in both groups, and the reductions were slightly greater than in the corresponding pair-fed groups. We conclude that the effects on food intake, growth and reproductive performance that were seen after feeding rats defatted jojoba meal were due to the simmondsin content of the meal. The simmondsin induced reduction in food intake and probably also a relative protein shortage.

Acetonitriles↗
PubMed1998

In ovo treatment with an aromatase inhibitor masculinizes postnatal hormone levels, abdominal fat pad content, and GH pulsatility in broiler chickens.

Vorozole, a selective aromatase inhibitor, was administered in ovo to test the specific embryonic role of estrogen in conferring the sex distinction in GH release and body phenotype in broilers. On Day 6 of incubation, eggs were injected with saline or with different concentrations of vorozole. Postnatal blood samples were analyzed for T3, T4, GH, estradiol (E2), and testosterone (T). At the age of 4 wk, control and vorozole-treated birds were cannulated, and serial blood samples were withdrawn every 10 min for 5 hr, wherein GH pulsatility characteristics were determined using deconvolution analysis. The proportional abdominal fat pad weight was reduced significantly in the treated groups, especially in female birds. The vorozole treatment increased plasma T3, E2, T, and GH concentrations, and decreased T4. The frequency of the GH pulses was lower and the interval between the bursts (min) was higher in the vorozole-treated group, as were the mass secreted per burst (ng/ml), the amplitude (ng/ml/min) and the production rate (ng/ml/5 hr). In conclusion, early in ovo treatment with a potent aromatase inhibitor is able to increase the mean serum T3 and GH concentration and masculinize the GH pulse pattern, resulting in an economically favorable decrease in abdominal fat pad content in male and female broilers at slaughter age.

Adipose Tissue↗